Depth, pressure and squeeze

[tylerz]

Maybe this is caused by very violent contractions at depth, even if the lung volume is still above RV this could create a lot of sudden negative pressure.

In Perry's case, and my other friend's case, contractions were not occurring. Interestingly, we discovered at one point that Perry could do free immersion without getting the squeeze but as soon as he finned down, he would get it. I don't know if later free immersion also caused it, but definately at one point that was not the case. I should contact him and find out.

 

[efattah]

In my experience doing free immersion increases the risk of squeeze, as does extending the arms on the ascent or descent, as does doing no-fins arm strokes at depth. Any movement or stretching of the rib cage from physical movements causes increased strain on my collapsed ribcage. Perry's case seems to contradict that though.

 

[tylerz]

In my experience doing free immersion increases the risk of squeeze, as does extending the arms on the ascent or descent, as does doing no-fins arm strokes at depth. Any movement or stretching of the rib cage from physical movements causes increased strain on my collapsed ribcage. Perry's case seems to contradict that though.

And interestingly, by these comments you may be inadvertently emphasizing that rate of pressure change is potentially a large factor in these cases. We already stated that in some of these cases they are not below RV, therefore no collapsed ribcage, which suggests gradual stretching/lengthing of the lungs to a degree that puts stress on the alveoli and/or the lungs is not the main factor. This emphasizes that extension of the arms would not be the factor in their cases as well.

However, I had been trying to suggest to Perry that it was his poor finning technique and possibly that he was becoming very rigid during his technique. Afterall, it was watching his technique that made me think to tell him to try free immersion, imagining that it would have a more relaxed and less stressful effect on his body. So, it occurs to me more clearly now, that my intuition at the time sensed, that maybe it was sudden changes in pressure due to awkward and fast finning. His body's response to that, mixed with probably poor flexibility in the first place may have allowed for rapid and significant changes in pressure. Free immersion allowed him to relax and therefore even though it caused more expansion of the lungs, his lung expansion vs. ambient pressure was probably never the problem in and of itself. The rate of change in these opposing forces was so gradual that everything was fine.

Thoughts?

 

[Bill]

"- beyond the third decade of life RV increases due to dynamic compression or closure of airways.
- as a fraction of TLC RV increases from 25% at 20 years to 40% at 70 yrs"

These are probably averages. I believe that the Vr/Vt increase is mostly related to the decrease of Vt which occurs from lack of use. I'm not 70 yet but the Vr seems constant even as my Vt increases a little from packing and stretching. It would be very interesting to check the ratio of one of the super 70 yo athletes that compete in the Iron Man or one of the spearfishing group that has been diving for 60+ years. Maybe Dr. Maas will share his numbers or some one can get access to the research data collected here every year.
Use it or lose it
Bill

 

[fpernett]

I may be off-track here, but my understanding is that RV is determined by the limit to which the ribcage/diaphragm can be compressed by ambient pressure before resistance increases to the point where the pressure differential between the space in the lungs and the ambient pressure has to be equalised in another way - by liquid first filling the alveoli forming the walls of the lung cavity and then forcing its way through them (causing damage) into the space itself.

I don't understand RV to be an attribute of the lung tissue itself (please correct me if this is wrong). The term 'RV' as it is commonly used seems to me to mean "lung volume following forceful exhale without other mechanical aid" and as such is reliant on the force supplied by the breathing muscles as well as the flexibility of the diaphragm/ribcage. Given adequate mechanical force (over and above that supplied solely by the breathing muscles) RV for everybody would be zero. Given sufficient bloodshift even in a thoracic inflexible person, RV would also be zero. Obviously this would mean a nasty injury in both cases because nobody is that flexible/nobody's alveolic can take that much engorgement, it's just my way of suggesting RV is not an absolute value unless you add the above condition.

RV depends of pulmonary and extra-pulmonary variables. As you pointed out, a person with a very strong diaphragm and very flexible thorax has a lower RV than a person without that conditions, but there is also intra-alveolar pressure that depends on surfactant, compliance and patency of the airway that communicates with it, this is refered as the Times Constant, so there is slow and fast alveoli (to empty and to fill). Persons with problems like asthma can have a increased RV during crisis, because the alveoli can't get empty on a normal exhalation.
I think is very difficult to reach values below RV, in fact RV can vary within the same individual. Blood-shift help you out to reach a lower RV without pulmonary collapse. When you pack the VC increases and RV decreases, but this is just an static measure. Nobody has measured Lung volumes during real immersion, and in the other hands, we don't know the long time effects of frequent lung packing, if, and this is purely theoretical, after frequent lung packing we loss elastic recoil of the lung, our RV can increase due to this practice.

Would reverse packing reduce the risk of squeeze? If packing increases RV, then reverse packing would surely reduce it?

Just an idea...

At least in theory it could be true. I´m living far away from places to practice real CW training, so in the 2 or 3 times in the year that can get to deep places I was posing my self in risk for immersion pulmonary edema (I got once to a ridiculous depth of 30 mts), so I started an slow and progressive training with reverse packing in the pool, and until now it has worked, but I think is more due to improve in chest flexibility, but can't discard some kind of thickening in my blood vessels.

My hypothesis is that things break around the trachea area and that fluids goes down into lung and causes near drowning symptoms (described).

I do believe, that in some cases the blood comes from the trachea, but for this blood to produce low oxygen saturation it has to be A LOT. I do Bronchoalveolar lavages to patients and some times I put and amount of saline solution of around 300-400 ml. without oxygenation problems. So the amount of blood to flood the lungs and produce near drowning has to be huge, more than just a spit with traces of blood.
As Sebastian said, this is quite confusing, because we don't have enough information, his suggestion to report it to DAN is a good start.
But after the information I had, contractions and excessive lung volumes prior to immersion are the main causes (just my opinion) the other is the fast progression without training on extreme volumes changes.

 

[larsemil]

allthough i have noticed with myself that i spit blood more oftendoing CWT then FIM, i think it has something to do with getting more tired, because of bad swimming technique.. also i stopped packing this season and diving unpacked feels much better.
my frcdives - wich gives more pressure on my trachea does not even make me caugh, just feels fine.

I also heard that being stressed at depth would be a reason to get squeeze. packing increases the heartrate...

 

[bolts]

Just a few notes about my (limited) experiences....

First last fall I got a bit of a squeeze, although it's unclear exactly where the blood was coming from, there was a bit of it in my spit. Along with this, it felt as if a heavy weight was placed on my chest, and I was a bit short of breath. After getting out of the water, the symptoms eased, and I felt ok, but didn't dive again for a few weeks. I chalked it up to a too-short warm-up, plus I remember using my arms to propel myself at depth (only about 15m or so...), which may or may not have irritated something.

Then this May I had my first dive, thought I did a decent warmup (at least I thought) and took procautions, and for the next few weeks it felt as if my chest was congested. Still to this day the symptoms come and go. The feeling is different than that described previously. I did notice a small speck or two of blood in my spit after diving, and noticed a slight wheeze when exhaling after getting out of the water. Plus, the next day, my ribs were sore all around, like someone went 12 rounds on them. :head This time I again used my arms at depth, just once, but I wonder if this may have irritated something. The water was somewhat cold as well, which may have contributed. I'd tend to believe I did something to my throat/trachea this time around. It's not so much alarming or painful as it is just an annoying feeling.

A few things I've found that help, thus far....doing a full slow warm up of pulldowns and a negative dive, if possible, to your comfort level. Plus, I now try to avoid all arm-propulsion movement at depth. Also, I've found that not taking a really deep breath before diving, in other words, not quite full lungs to capacity. Seems to be less stressful that way.

 

[bolts]

Just an update.... I just got back from a day of diving and reached a new PB of 85ish feet (analog gauge...). For me, that's huge!

However...that dive where I set the PB saw me coughing up a little bit of blood. :rcard However, the sensation isn't the same as before, there's no heaviness in the chest upon inhaling or wheezing at all, just a little bit of blood if I force a cough. In the time immediately proceeding the dive, there was enough blood to freak me out a bit though... Otherwise, I feel ok, but I'm going to keep an eye on it.

My warm up was lengthy (several pulldowns to 10m then 15m or so) plus some negative dives (to about 3m or so...can't get down much more than that, mainly due to equalization issues on empty lungs).

A few things:

-I increased my PB by about 15 feet (5m or so), so that probably contributed greatly to it.
-I seem to recall looking up at depth, which may have stretched my trachea, at least that's what my buddy and I thought.

Lesson here is...take your time, be patient, not like me. I'm trying to learn to take it slowly, but it's so tempting to push your limits, not knowing where they are until it's too late.:head